Re: [boost] Using operators.hpp

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-10-31 22:53:27

Hi Bill,

You're not missing anything. The Barton&Nackmann trick used by the operators
library can only provide concrete non-templated operators (dependent on the
template parameters of the derived template), not generalized operators
which would have to be supplied by a templated operator, e.g.:

template <class L, class R>
decimal<(L>R?L:R)> operator+(decimal<L> const&, decimal<R> const&)
{
    // whatever...
}

HTH,
Dave

===================================================
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          email: david.abrahams_at_[hidden]
===================================================

----- Original Message -----
From: "Bill Seymour" <bill-at-the-office_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, October 31, 2001 11:23 AM
Subject: [boost] Using operators.hpp

> Last weekend in Redmond, Beman told me that one objection
> to the fixed-point decimal library was that I hadn't used
> operators.hpp.  I said that I had looked at it once and
> my first impression was that it offered more pain than
> gain; but I promised to look at it again.
>
> OK, I'm trying to apply this to the decimal<> class;
> and so far I've written:
>
>   template<int Precision = 0>
>   class decimal
>     : unit_steppable< decimal<Precision>
>     , arithmetic2< decimal<Precision>, int
>     , arithmetic2< decimal<Precision>, decimal<?>
>     , arithmetic2< decimal<Precision>, rounding_proxy< decimal<?> >
>       > > > >
>
> Note the two occurrances of decimal<?>.  I don't understand
> how to say "decimal<some other precision>" here.  What am I
> missing?
>
> Thanks,
>
> --Bill Seymour
>
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